Addison's disease, or hypoadrenocorticism, is a disease characterized by adrenal insufficiency, or the inability of the adrenal glands to produce adequate levels of certain hormones to maintain health. The disease is not common in dogs and affects younger, female dogs most often. Generally, Addison's Disease is treated with Florinef or its generic alternative, Fludrocortisone Acetate.
Types and Causes of Addison's Disease in Dogs
The adrenal glands consist of two layers, the cortex and medulla, and are located in the abdomen, directly adjacent to the kidneys. The cortex secretes cortisol, aldosterone, and other corticosteroid hormones, and the medulla secretes epinephrine. Damage to one or both layers of the adrenal glands is responsible for Addison's disease in dogs. In most cases, Addison's disease only affects the cortex.
"Recognizing Addison's disease is difficult because the symptoms overlap with other conditions."
Addison's disease may exist in three forms: atypical, primary, and secondary. Atypical and primary diseases generally result from damage to the adrenal glands by the immune system. Secondary Addison's disease occurs when the pituitary gland fails to stimulate the adrenal glands with a hormone called ACTH. This hormone tells the adrenal glands to produce cortisol. Certain medications, infections, and cancers may contribute to the development of Addison's. Abruptly stopping long-term steroid use may also trigger the onset of the disease in some dogs.
Recognizing the Symptoms of Canine Addison's Disease
Recognizing Addison's disease in dogs is difficult for many pet owners and veterinarians because the symptoms are often vague and overlap with other health conditions. Initially, listlessness or mild depression may be the only sign that something is wrong. Some dogs may experience reduced appetite. In some cases, diarrhea, vomiting, excessive thirst, muscle weakness, and shivering may develop, and symptoms may become more pronounced during times of stress. Symptoms may come and go over months or years, making it even more difficult to identify the underlying problem.
At some point, canine Addison's disease will trigger an acute episode of illness called an Addisonian crisis. During this episode, potassium levels elevate to the point of triggering heart dysfunction, which in turn can dangerously lower blood pressure. Creatinine and BUN levels increase and kidney failure may occur. While it may seem like an Addisonian crisis is an unmistakable sign of Addison's disease, rehydration generally stops the crisis rapidly, leading caretakers to believe that dehydration or another cause are responsible for the symptoms.
Diagnosing Addison's in Dogs
Only a few tests are helpful in making a diagnosis of Addison's. Your veterinarian will likely test your dog's electrolyte levels to determine the ratio of sodium to potassium. Dogs with Addison's typically have low sodium levels, high potassium levels, and a low ratio between the two. Another test, called the ACTH stimulation test, determines whether the adrenal glands are able to produce cortisol.
Even with positive test results, Addison's disease is often difficult to diagnose because the condition causes symptoms common to many other health conditions. For this reason, a diagnosis is typically made only after eliminating other possible causes of electrolyte imbalance, poor appetite and weight gain, and other symptoms.
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